This invention relates to axial flow rotary separators for agricultural crops of a kind typically embodied in combines and more particularly to material control and conveying elements carried on the rotors of such separators.
The mode of operation of such separators is well known. Crop material is fed into the annular space between a rotor and a stationary housing, which includes grate portions, and through cooperation between rotor and housing the material is propelled in a spiral path through the annular space while grain is threshed and separated from it and expelled through the grates and collected for further processing. Typically the rotor includes a first, upstream feed rotor portion designed to receive crop material from a feeder house and convey it into the separator proper.
The internal surface of the housing and the external surface of the rotor are provided with material control elements or features so that the relative motion between the rotor and housing surfaces effects the processing and conveying of the material contained between them. The material control elements used in existing separators vary in detail but, typically, axial indexing is effected by generally helical ribs (either continuous or interrupted) carried usually by the housing but sometimes by the rotor or by both. The rotor typically carries generally axially extending elements which have primarily a processing function and only secondarily a conveying function and may include conventional rasp bars in the threshing section and paddles in a separating section. The general form of these elements, particularly those on the rotor, is radially extending with respect to the axis of the rotor. These relatively simple and conventional forms of material control elements can be combined fairly readily to produce axial flow rotary separator designs which perform well in a limited range of crops or crop conditions, for example handling corn and soybeans at moderate moisture contents. However, there is a tendency with conventional material control elements and particularly those of generally radial extent for crop material to collect into "ropes" or fold into wads in advance of the elements, tending to jam or wedge between the rotor and housing and causing serious fluctuations in torque in the rotor drive system (if not actually plugging the machine) and reducing threshing and separating efficiency because of the undesirable bunching of material. The tendency for these conventional material control elements to actually lose control of material is especially pronounced in handling the more difficult crop materials, particularly long straw varieties at high moisture contents and especially rice.
A particular problem in axial flow rotary separators is to transform, in as short an axial space as possible, a concentrated stream of crop material delivered by a feeder house into a thin annular mat for efficient reception into the relatively confined annular space of the threshing zone. It is known to provide a stepped grate or concave to permit increased grate or concave clearance at the beginning of the threshing section and also to provide specially designed feed rotor flights in attempts to overcome this problem.
Combines embodying axial flow rotary separators potentially have high specific capacity and versatility but with the material control elements and systems so far known, these potentials have been only partially realized.